Waveguides, which are known to be used in microwave technology, have various lengths, cross-sectional shapes and sizes. Hollow waveguides often have rectangular cross sections. However, round cross-sectional shapes are also known. Conventionally, waveguides of this type are equipped at the start and at the end with a flange so to join rigidly together successive waveguide portions. In a waveguide path, the cross section is usually maintained. However, transitions from one cross-sectional shape to another cross-sectional shape are also known.
It is often necessary to provide a change in a direction in a waveguide path. What are known as waveguide bends or waveguide angles are used for this purpose. Usually, these are 90° bends which change the direction of the lines of electric flux (E bends, E angles), i.e. in the case of rectangular waveguides via the broad side, or the direction of the lines of magnetic flux (H bends, H angles), i.e. in the case of rectangular waveguides in the direction of the narrow side.
Waveguide bends of this type are basically known from the publication by Erich Pehl, “Mikrowellentechnik, Band 1, Wellenleitungen und Leitungsbausteine”, Dr Alfred Hütig Verlag Heidelberg, 1988, pages 172 to 175 and, for example, from Walter Jansen, “Hohlleiter und Streifenleiter”, Dr Alfred Hütig Verlag Heidelberg, 1977, pages 101 to 104. The above-mentioned prior publication by Walter Jansen reproduces in this regard with reference to FIG. 6.1 b is known as an H bend and with reference to drawing 6.1 c is known as an E bend.
A 90° waveguide bend has also become known from EP 0 285 295 A1, in which the waveguide bend has an edge length is specified as 0.900 inch. For optimizing the waveguide bend while reducing absorbability, it is specified that the length L from the start of the chamfer up to the 90° corner point should, for optimizing the E plane waves, be 0.700 inch and, for optimizing the H plane wave, be 0.642 inch for an edge length of the waveguide cross section of 0.900 inch.
Exemplary illustrative non-limiting implementations herein provide a waveguide which has a square cross section and a 90° waveguide bend, i.e. a 90° waveguide angle, which can be manufactured by casting in which cost-effective and reliable adaptation to existing LNBs are possible, with electrical properties again improved over the prior art with regard to the propagation of the electromagnetic waves (i.e. both the E and the H plane waves) in the waveguide.
An exemplary illustrative non-limiting implementation provides a 90° waveguide bend which, due to its square waveguide cross section, can be used either as an E bend for lines of electric flux or as an H bend for lines of magnetic flux.
In an exemplary illustrative square waveguide, two modes, which are orthogonal to each other, are capable of propagation. In the case of a 90° bend of this type having a square cross section, reflections and transit absorptions can occur which in turn can yield insufficient electrical values for practical use.
To overcome these undesirable characteristics, it is conventional to guide both modes positioned perpendicularly to each other separately via their own rectangular waveguides or both modes jointly via a round waveguide. A round waveguide has in this case a drawback of requiring relatively large bend radii, i.e. a space-saving 90° bend cannot be carried out.
An exemplary illustrative non-limiting 90° waveguide bend is particularly suited to a frequency range of 10.7 to 12.75 GHz in both vertical and horizontal polarizations (parallel orientation to both the axes positioned perpendicularly to one another of the quadratic cross section of the waveguide).
The exemplary illustrative waveguide bend can also be applied to other frequency ranges of comparable relative bandwidth (about +/−10% based on the center frequency). A factor to consider is the edge length of the waveguide, which is then to be scaled accordingly. For the specified frequency range, the edge length is, for example, 15 mm.
Exemplary illustrative non-limiting implementations provide a 90° waveguide bend which has good electrical transmission properties, including cross-polarization decoupling, for both polarizations.
For implementing 90° waveguides of this type, it has already been proposed to configure the transition as a continuous curved portion (i.e. in side elevation as a partially circular rectangular tube).
However, conventional practice is for the two waveguide portions being configured perpendicularly to each other to be connected in the 90° bend region in such a way that the connecting side external to the internal 90° corner point has an edge length of a√{square root over (2)}, “a” being the edge length of the square waveguide. The length of the bending therefore corresponds to a diagonal in a square having the edge length “a”.
Exemplary illustrative non-limiting implementations propose a differing geometry in which the chamfer of the compensated corner in the 90° bend region corresponds to the edge length a of a square waveguide, wherein slight deviations of less than 0.1% can still be regarded as being sufficient.
Preferably, the above-mentioned dimension rule is applied to the internal dimension of the waveguide and not the external lengths in view of the wall thicknesses. The square waveguide has in this case on its connectors as its clear internal dimension the edge length “a”. The chamfered wall in the angular range preferably also has as its internal dimension a length in the direction of propagation of the electromagnetic waves corresponding to the dimension a of the clear distance at the connectors which are square in cross section.
Exemplary illustrative non-limiting implementations relate to a 90° bend, but this bend does not necessarily have to be precisely 90°. It may, in principle, also be a bend designed for an angular range between 70° and 110°, more preferably for an angular range between 80° and 100° or, even more preferable still, for an angular range between 85° and 95°.
Although a 90° waveguide bend has in principle also become known from U.S. Pat. No. 6,253,444 B1, this waveguide bend has, in contrast to the subject-matter herein, a rectangular cross section rather than a square cross section. In addition, this prior publication has shown it to be fundamental that the waveguide bend does not have in the region of transition a chamfer comparable to the technology herein; instead, stepped shoulders are incorporated into the waveguide material. These may be in the form of a few large steps or a large number of steps, the height of which decreases as the number of steps increases. Nevertheless, the technology herein has revealed that an embodiment of this type does not lead to the desired properties such as may be achieved within exemplary illustrative non-limiting implementations herein.